The WIZ820io/WIZ850io can be purchased from Mouser Electronics, Digikey, Saelig and other
electronic component distributors. Inexpensive WIZ850io
clones can be found on Ebay or
Aliexpress. PJRC does not sell the any these ethernet modules.

WIZ850io (W5500 chip) should be used for new designs. WIZ850io has all the features
of the older WIZ820io (W5200), with lower power consumption, and at lower cost.

Reset Signal

WIZ820io requires a reset pulse to function properly.
WIZ850io is more tolerant of startup without reset, but a pulse on the reset
pin is absolutely required for the older WIZ820io modules.

This adaptor has a CAT811T reset chip to automatically pulse reset at powerup.
However, after uploading a new program, your WIZ820io may be left in a prior state
depending on where your prior program stopped. Pin 9 should be used to manually
trigger the reset pulse for best compatibility with WIZ820io and W5200 chips.
See the initialization code below for an example.

Rev 2 - Easier SPI Sharing

A second revision adds pullup resistors on pins 4, 9 and 10, and a reset
chip for the WIZ820io.

These resistors keep the SD card and WIZ820io/WIZ850io from responding to other
SPI communication. Some WIZ820io can disrupt SPI communication before
being reset, even of their chip select pin is pulled high. The new
reset chip guarantees proper reset at startup, even if the recommended
code below is not used.

Recommended Assembly Steps

Place the header pins in a breadboard or other fixture to hold them
straight and at the correct spacing. Position the WIZ820_SD_ADAPTOR
on the pins.

Trim the 12 inner pins next to the WIZ820 pads.

Solder the 28 header pins to the WIZ820_SD_ADAPTOR.

Solder the 12 WIZ820io pin to the WIZ820_SD_ADAPTOR.

Optionally, the WIZ820io pins can be placed into sockets and the sockets soldered
to the WIZ820_SD_ADAPTOR, to allow the WIZ820io to be removed.

Solder the 28 header pins to Teensy 3.x.

Optionally, the header pins can be placed into
sockets and the sockets soldered
to the Teensy 3.x.

After assembly, the stack of boards should look like this:

Electrical Connections

This table lists the electrical connections on this adaptor board.

The WIZ820io and SD card are connected to the default pins used by
the Arduino Ethernet and SD libraries. For the SD library, pin 4
should be used in the begin() function.

By default, the center and right side of the jumper pads are connected,
which keeps the WIZ820io powered up. For low power applications, the
pads can be cut apart and the left+center joined to allow pin 8 to control
the WIZ820io/WIZ850io powerdown feature.